With development of display techniques, flexible display devices are currently merging into people's life. The flexible display devices are characterized in foldability. However, a user often desires a shape of a flexible display device to be kept in a certain state in the process of using the flexible display device, and to be folded when not using the flexible display device. Current flexible display techniques cannot meet requirements that a flexible display screen is completed folded up or has a very small curvature radius. However, the user may tend to bend or fold up the flexible display device to an extent that the curvature radius of a portion of the flexible display screen is too small, or even the flexible display screen is completed folded up, thus damaging the flexible display screen.